Alkali resistant catalyst

a technology of alkali resistant catalyst and catalyst, which is applied in the direction of catalyst activation/preparation, metal/metal-oxide/metal-hydroxide catalyst, etc., can solve the problems of nox being harmful to human and animal health, catalysts not suitable for nox of flue gases containing large amounts of alkali, and reducing catalytic activity

Inactive Publication Date: 2009-11-19
DANMARKS TEKNISKE UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a process for selectively removing nitrogen oxides from gases containing a significant amount of alkali metal and / or alkali-earth compounds using a catalyst. The catalyst consists of a formed porous superacidic support and a metal oxide catalytic component deposited on the support, such as copper, vanadium, iron, chromium, manganese, or mixtures thereof. The technical effect of this invention is to provide a more efficient and effective method for removing nitrogen oxides from gases containing these compounds.

Problems solved by technology

Unfortunately, alkali metals and earth alkali metals are present in relatively large amounts in flue gases from burning of biomass or biomass fuel such as straw, woodchips and wood pellets.
Generally, NOx is an environmental problem, including acid rain formation; NOx is also considered to be harmful for human and animal health.
However, these catalysts are not suitable for SCR of NOx of flue gases containing large amount of alkali and earth alkali metals, such as flue gases from biomass fuels.
When these conventional catalysts are loaded with alkali earth metals or alkali metals, especially with potassium, this results in (i) a considerable decrease of catalytic activity, as well as (ii) to a shift of the maximum catalytic activity towards lower temperatures, both features that are highly undesired.
In particular, the relative activity of a vanadium based catalyst decreases severely when the catalyst is poisoned with alkali metals.
The severity of deactiation is proportional to the basicity of the metal oxides, where potassium oxide—due to its significant presence in the biomass fly ash combined with its high basicity—commonly constitutes the main problem.
However, a drawback in the use of vanadium-based catalysts in the SCR of flue gases from biomass is that vanadium is both more expensive and, except for Cr, more toxic than many other catalysts.

Method used

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Embodiment Construction

[0026]One aspect of the present invention concerns a process for the selective removal of nitrogen oxides in the presence of ammonia from gases containing a significant amount of alkali metal and / or alkali-earth compounds which process comprises using a catalyst combined of[0027]a) a formed porous superacidic support[0028]b) a metal oxide catalytic component deposited on said support selected from the group consisting of Cu, Fe, V, Cr, Mn, and any mixtures thereof.

[0029]Another aspect of the invention relates to a catalyst in the process of the selective removal of nitrogen oxides in the presence of ammonia from gases containing a significant amount of alkali metal and / or alkali-earth compounds which process comprises using a catalyst combined of[0030]a) a formed porous superacidic support[0031]b) a metal oxide catalytic component deposited on said support selected from the group consisting of Cu, Fe, V, Cr, Mn, and any mixtures thereof.

[0032]A further aspect of the invention pertai...

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Abstract

The present invention concerns the selective removal of nitrogen oxides (NOx) from gasses. In particular, the invention concerns a process, a catalyst and the use of a catalyst for the selective removal of nitrogen oxides in the presence of ammonia from gases containing a significant amount of alkali metal and / or alkali-earth compounds which process comprises using a catalyst combined of (i) a formed porous superacidic support, said superacidic support having an Hammett acidity stronger than Ho=−12, and (ii) a metal oxide catalytic component deposited on said superacidic support selected from the group consisting of oxides of Fe, Cu, V, Cr, Mn, and any mixtures thereof.

Description

FIELD OF THE INVENTION[0001]The present invention concerns the selective removal of nitrogen oxides (NOx) from gasses. In particular, the invention concerns a process, a catalyst and the use of a catalyst for removal of NOx from exhaust or flue gases, said gases comprising alkali or earth alkali metals. Such gases comprise for example flue gases arising from the burning of biomass, combined biomass and fossil fuel, and from waste incineration units. The process comprises the selective catalytic reduction (SCR) of NOx, such as nitrogen dioxide (NO2) and nitrogen oxide (NO) with ammonia (NH3) as reductant.BACKGROUND OF THE INVENTION[0002]The use of biomass fuels is considered more and more advantageous, as biomass fuels are CO2 neutral, i.e. they discharge the same amount CO2 when burned, as they absorbed from the air while growing. Unfortunately, alkali metals and earth alkali metals are present in relatively large amounts in flue gases from burning of biomass or biomass fuel such as...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): B01D53/56B01J23/34B01J23/26B01J23/745B01J23/72B01J23/22
CPCB01D53/8628B01J37/20B01D2255/20723B01D2255/2073B01D2255/20738B01D2255/20761B01D2255/20769B01D2255/9205B01D2255/9207B01J21/063B01J21/066B01J23/22B01J23/72B01J23/745B01J27/053B01D2251/2062
InventorRASMUSSEN, SOREN BIRKKUSTOV, ARKADYFEHMANN, RASMUSDUE-HANSEN, JOHANNES
OwnerDANMARKS TEKNISKE UNIV